The invention relates to a heat exchanger for transferring heat from a dust-containing gaseous medium, e.g. air or other gas, to a second fluent medium, such as air, the two media being kept separate from one another. A known kind of such heat exchanger (hereinafter referred to as of the kind described) consists of a housing, with a preferably rectangular cross-section. At the upper part of the housing are provided a gas inlet and a gas outlet, between which is provided for the gaseous medium a U-shaped path through the housing, the path being partly defined by a partition wall suspended from a top plate of the housing. A number of U-shaped pipes, the individual ends of which are secured to the top plate, at the upper side of which they open upon opposite sides of the suspended partition, are mounted in the U-shaped path and form a path for the second medium which is fed through the pipes. Two chambers with an inlet and an outlet, respectively, are provided above the pipe ends, one on each side of the partition. The partition walls, the chambers and the top plate constitute a top section of the heat exchanger. Such heat exchangers with suspended U-shaped pipes in a U-shaped path are in principle known for instance from No. DE-A-28 46 581.
When a heat exchanger of the kind described is used for cooling dust-containing gases or recovering heat therefrom, the gases are passed along the U-shaped path through the housing, while the cooling medium or the carrying medium for the recovered heat is passed through the U-shaped pipes countercurrently to the gas flow through the housing along its U-shaped path. On its way through the housing some of the dust is precipitated, and the housing is provided at its bottom with a discharge hopper for precipitated dust.
Part of the dust, however, settles on the pipes and impairs the heat transfer from one medium to the other, and it is necessary from time to time to clean the pipes of precipitated dust. Normally this is done by stopping the plant for some time while purely mechanical cleaning of the pipes is effected, e.g. by blowing them clean by pressurized air, possibly with the addition of some kind of abrasive grain.
It is the object of the invention to devise a heat exchanger of the kind described by which the pipes can be kept constantly clean during uninterrupted operation of the heat exchanger.